/usr/share/gocode/src/github.com/weaveworks/mesh/peers.go is in golang-github-weaveworks-mesh-dev 0+git20161024.3dd75b1-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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import (
"bytes"
"encoding/gob"
"io"
"math/rand"
"sync"
)
// Peers collects all of the known peers in the mesh, including ourself.
type Peers struct {
sync.RWMutex
ourself *localPeer
byName map[PeerName]*Peer
byShortID map[PeerShortID]shortIDPeers
onGC []func(*Peer)
// Called when the mapping from short IDs to peers changes
onInvalidateShortIDs []func()
}
type shortIDPeers struct {
// If we know about a single peer with the short ID, this is
// that peer. If there is a collision, this is the peer with
// the lowest Name.
peer *Peer
// In case of a collision, this holds the other peers.
others []*Peer
}
type peerNameSet map[PeerName]struct{}
type connectionSummary struct {
NameByte []byte
RemoteTCPAddr string
Outbound bool
Established bool
}
// Due to changes to Peers that need to be sent out
// once the Peers is unlocked.
type peersPendingNotifications struct {
// Peers that have been GCed
removed []*Peer
// The mapping from short IDs to peers changed
invalidateShortIDs bool
// The local short ID needs reassigning due to a collision
reassignLocalShortID bool
// The local peer was modified
localPeerModified bool
}
func newPeers(ourself *localPeer) *Peers {
peers := &Peers{
ourself: ourself,
byName: make(map[PeerName]*Peer),
byShortID: make(map[PeerShortID]shortIDPeers),
}
peers.fetchWithDefault(ourself.Peer)
return peers
}
// Descriptions returns descriptions for all known peers.
func (peers *Peers) Descriptions() []PeerDescription {
peers.RLock()
defer peers.RUnlock()
descriptions := make([]PeerDescription, 0, len(peers.byName))
for _, peer := range peers.byName {
descriptions = append(descriptions, PeerDescription{
Name: peer.Name,
NickName: peer.peerSummary.NickName,
UID: peer.UID,
Self: peer.Name == peers.ourself.Name,
NumConnections: len(peer.connections),
})
}
return descriptions
}
// OnGC adds a new function to be set of functions that will be executed on
// all subsequent GC runs, receiving the GC'd peer.
func (peers *Peers) OnGC(callback func(*Peer)) {
peers.Lock()
defer peers.Unlock()
// Although the array underlying peers.onGC might be accessed
// without holding the lock in unlockAndNotify, we don't
// support removing callbacks, so a simple append here is
// safe.
peers.onGC = append(peers.onGC, callback)
}
// OnInvalidateShortIDs adds a new function to a set of functions that will be
// executed on all subsequent GC runs, when the mapping from short IDs to
// peers has changed.
func (peers *Peers) OnInvalidateShortIDs(callback func()) {
peers.Lock()
defer peers.Unlock()
// Safe, as in OnGC
peers.onInvalidateShortIDs = append(peers.onInvalidateShortIDs, callback)
}
func (peers *Peers) unlockAndNotify(pending *peersPendingNotifications) {
broadcastLocalPeer := (pending.reassignLocalShortID && peers.reassignLocalShortID(pending)) || pending.localPeerModified
onGC := peers.onGC
onInvalidateShortIDs := peers.onInvalidateShortIDs
peers.Unlock()
if pending.removed != nil {
for _, callback := range onGC {
for _, peer := range pending.removed {
callback(peer)
}
}
}
if pending.invalidateShortIDs {
for _, callback := range onInvalidateShortIDs {
callback()
}
}
if broadcastLocalPeer {
peers.ourself.broadcastPeerUpdate()
}
}
func (peers *Peers) addByShortID(peer *Peer, pending *peersPendingNotifications) {
if !peer.HasShortID {
return
}
entry, ok := peers.byShortID[peer.ShortID]
if !ok {
entry = shortIDPeers{peer: peer}
} else if entry.peer == nil {
// This short ID is free, but was used in the past.
// Because we are reusing it, it's an invalidation
// event.
entry.peer = peer
pending.invalidateShortIDs = true
} else if peer.Name < entry.peer.Name {
// Short ID collision, this peer becomes the principal
// peer for the short ID, bumping the previous one
// into others.
if entry.peer == peers.ourself.Peer {
// The bumped peer is peers.ourself, so we
// need to look for a new short ID.
pending.reassignLocalShortID = true
}
entry.others = append(entry.others, entry.peer)
entry.peer = peer
pending.invalidateShortIDs = true
} else {
// Short ID collision, this peer is secondary
entry.others = append(entry.others, peer)
}
peers.byShortID[peer.ShortID] = entry
}
func (peers *Peers) deleteByShortID(peer *Peer, pending *peersPendingNotifications) {
if !peer.HasShortID {
return
}
entry := peers.byShortID[peer.ShortID]
var otherIndex int
if peer != entry.peer {
// peer is secondary, find its index in others
otherIndex = -1
for i, other := range entry.others {
if peer == other {
otherIndex = i
break
}
}
if otherIndex < 0 {
return
}
} else if len(entry.others) != 0 {
// need to find the peer with the lowest name to
// become the new principal one
otherIndex = 0
minName := entry.others[0].Name
for i := 1; i < len(entry.others); i++ {
otherName := entry.others[i].Name
if otherName < minName {
minName = otherName
otherIndex = i
}
}
entry.peer = entry.others[otherIndex]
pending.invalidateShortIDs = true
} else {
// This is the last peer with the short ID. We clear
// the entry, don't delete it, in order to detect when
// it gets re-used.
peers.byShortID[peer.ShortID] = shortIDPeers{}
return
}
entry.others[otherIndex] = entry.others[len(entry.others)-1]
entry.others = entry.others[:len(entry.others)-1]
peers.byShortID[peer.ShortID] = entry
}
func (peers *Peers) reassignLocalShortID(pending *peersPendingNotifications) bool {
newShortID, ok := peers.chooseShortID()
if ok {
peers.setLocalShortID(newShortID, pending)
return true
}
// Otherwise we'll try again later on in garbageColleect
return false
}
func (peers *Peers) setLocalShortID(newShortID PeerShortID, pending *peersPendingNotifications) {
peers.deleteByShortID(peers.ourself.Peer, pending)
peers.ourself.setShortID(newShortID)
peers.addByShortID(peers.ourself.Peer, pending)
}
// Choose an available short ID at random.
func (peers *Peers) chooseShortID() (PeerShortID, bool) {
rng := rand.New(rand.NewSource(int64(randUint64())))
// First, just try picking some short IDs at random, and
// seeing if they are available:
for i := 0; i < 10; i++ {
shortID := PeerShortID(rng.Intn(1 << peerShortIDBits))
if peers.byShortID[shortID].peer == nil {
return shortID, true
}
}
// Looks like most short IDs are used. So count the number of
// unused ones, and pick one at random.
available := int(1 << peerShortIDBits)
for _, entry := range peers.byShortID {
if entry.peer != nil {
available--
}
}
if available == 0 {
// All short IDs are used.
return 0, false
}
n := rng.Intn(available)
var i PeerShortID
for {
if peers.byShortID[i].peer == nil {
if n == 0 {
return i, true
}
n--
}
i++
}
}
// fetchWithDefault will use reference fields of the passed peer object to
// look up and return an existing, matching peer. If no matching peer is
// found, the passed peer is saved and returned.
func (peers *Peers) fetchWithDefault(peer *Peer) *Peer {
peers.Lock()
var pending peersPendingNotifications
defer peers.unlockAndNotify(&pending)
if existingPeer, found := peers.byName[peer.Name]; found {
existingPeer.localRefCount++
return existingPeer
}
peers.byName[peer.Name] = peer
peers.addByShortID(peer, &pending)
peer.localRefCount++
return peer
}
// Fetch returns a peer matching the passed name, without incrementing its
// refcount. If no matching peer is found, Fetch returns nil.
func (peers *Peers) Fetch(name PeerName) *Peer {
peers.RLock()
defer peers.RUnlock()
return peers.byName[name]
}
// Like fetch, but increments local refcount.
func (peers *Peers) fetchAndAddRef(name PeerName) *Peer {
peers.Lock()
defer peers.Unlock()
peer := peers.byName[name]
if peer != nil {
peer.localRefCount++
}
return peer
}
// FetchByShortID returns a peer matching the passed short ID.
// If no matching peer is found, FetchByShortID returns nil.
func (peers *Peers) FetchByShortID(shortID PeerShortID) *Peer {
peers.RLock()
defer peers.RUnlock()
return peers.byShortID[shortID].peer
}
// Dereference decrements the refcount of the matching peer.
// TODO(pb): this is an awkward way to use the mutex; consider refactoring
func (peers *Peers) dereference(peer *Peer) {
peers.Lock()
defer peers.Unlock()
peer.localRefCount--
}
func (peers *Peers) forEach(fun func(*Peer)) {
peers.RLock()
defer peers.RUnlock()
for _, peer := range peers.byName {
fun(peer)
}
}
// Merge an incoming update with our own topology.
//
// We add peers hitherto unknown to us, and update peers for which the
// update contains a more recent version than known to us. The return
// value is a) a representation of the received update, and b) an
// "improved" update containing just these new/updated elements.
func (peers *Peers) applyUpdate(update []byte) (peerNameSet, peerNameSet, error) {
peers.Lock()
var pending peersPendingNotifications
defer peers.unlockAndNotify(&pending)
newPeers, decodedUpdate, decodedConns, err := peers.decodeUpdate(update)
if err != nil {
return nil, nil, err
}
// Add new peers
for name, newPeer := range newPeers {
peers.byName[name] = newPeer
peers.addByShortID(newPeer, &pending)
}
// Now apply the updates
newUpdate := peers.applyDecodedUpdate(decodedUpdate, decodedConns, &pending)
peers.garbageCollect(&pending)
for _, peerRemoved := range pending.removed {
delete(newUpdate, peerRemoved.Name)
}
updateNames := make(peerNameSet)
for _, peer := range decodedUpdate {
updateNames[peer.Name] = struct{}{}
}
return updateNames, newUpdate, nil
}
func (peers *Peers) names() peerNameSet {
peers.RLock()
defer peers.RUnlock()
names := make(peerNameSet)
for name := range peers.byName {
names[name] = struct{}{}
}
return names
}
func (peers *Peers) encodePeers(names peerNameSet) []byte {
buf := new(bytes.Buffer)
enc := gob.NewEncoder(buf)
peers.RLock()
defer peers.RUnlock()
for name := range names {
if peer, found := peers.byName[name]; found {
if peer == peers.ourself.Peer {
peers.ourself.encode(enc)
} else {
peer.encode(enc)
}
}
}
return buf.Bytes()
}
// GarbageCollect takes a lock, triggers a GC, and invokes the accumulated GC
// callbacks.
func (peers *Peers) GarbageCollect() {
peers.Lock()
var pending peersPendingNotifications
defer peers.unlockAndNotify(&pending)
peers.garbageCollect(&pending)
}
func (peers *Peers) garbageCollect(pending *peersPendingNotifications) {
peers.ourself.RLock()
_, reached := peers.ourself.routes(nil, false)
peers.ourself.RUnlock()
for name, peer := range peers.byName {
if _, found := reached[peer.Name]; !found && peer.localRefCount == 0 {
delete(peers.byName, name)
peers.deleteByShortID(peer, pending)
pending.removed = append(pending.removed, peer)
}
}
if len(pending.removed) > 0 && peers.byShortID[peers.ourself.ShortID].peer != peers.ourself.Peer {
// The local peer doesn't own its short ID. Garbage
// collection might have freed some up, so try to
// reassign.
pending.reassignLocalShortID = true
}
}
func (peers *Peers) decodeUpdate(update []byte) (newPeers map[PeerName]*Peer, decodedUpdate []*Peer, decodedConns [][]connectionSummary, err error) {
newPeers = make(map[PeerName]*Peer)
decodedUpdate = []*Peer{}
decodedConns = [][]connectionSummary{}
decoder := gob.NewDecoder(bytes.NewReader(update))
for {
summary, connSummaries, decErr := decodePeer(decoder)
if decErr == io.EOF {
break
} else if decErr != nil {
err = decErr
return
}
newPeer := newPeerFromSummary(summary)
decodedUpdate = append(decodedUpdate, newPeer)
decodedConns = append(decodedConns, connSummaries)
if _, found := peers.byName[newPeer.Name]; !found {
newPeers[newPeer.Name] = newPeer
}
}
for _, connSummaries := range decodedConns {
for _, connSummary := range connSummaries {
remoteName := PeerNameFromBin(connSummary.NameByte)
if _, found := newPeers[remoteName]; found {
continue
}
if _, found := peers.byName[remoteName]; found {
continue
}
// Update refers to a peer which we have no knowledge of.
newPeers[remoteName] = newPeerPlaceholder(remoteName)
}
}
return
}
func (peers *Peers) applyDecodedUpdate(decodedUpdate []*Peer, decodedConns [][]connectionSummary, pending *peersPendingNotifications) peerNameSet {
newUpdate := make(peerNameSet)
for idx, newPeer := range decodedUpdate {
connSummaries := decodedConns[idx]
name := newPeer.Name
// guaranteed to find peer in the peers.byName
switch peer := peers.byName[name]; peer {
case peers.ourself.Peer:
if newPeer.UID != peer.UID {
// The update contains information about an old
// incarnation of ourselves. We increase our version
// number beyond that which we received, so our
// information supersedes the old one when it is
// received by other peers.
pending.localPeerModified = peers.ourself.setVersionBeyond(newPeer.Version)
}
case newPeer:
peer.connections = makeConnsMap(peer, connSummaries, peers.byName)
newUpdate[name] = struct{}{}
default: // existing peer
if newPeer.Version < peer.Version ||
(newPeer.Version == peer.Version &&
(newPeer.UID < peer.UID ||
(newPeer.UID == peer.UID &&
(!newPeer.HasShortID || peer.HasShortID)))) {
continue
}
peer.Version = newPeer.Version
peer.UID = newPeer.UID
peer.NickName = newPeer.NickName
peer.connections = makeConnsMap(peer, connSummaries, peers.byName)
if newPeer.ShortID != peer.ShortID || newPeer.HasShortID != peer.HasShortID {
peers.deleteByShortID(peer, pending)
peer.ShortID = newPeer.ShortID
peer.HasShortID = newPeer.HasShortID
peers.addByShortID(peer, pending)
}
newUpdate[name] = struct{}{}
}
}
return newUpdate
}
func (peer *Peer) encode(enc *gob.Encoder) {
if err := enc.Encode(peer.peerSummary); err != nil {
panic(err)
}
connSummaries := []connectionSummary{}
for _, conn := range peer.connections {
connSummaries = append(connSummaries, connectionSummary{
conn.Remote().NameByte,
conn.remoteTCPAddress(),
conn.isOutbound(),
conn.isEstablished(),
})
}
if err := enc.Encode(connSummaries); err != nil {
panic(err)
}
}
func decodePeer(dec *gob.Decoder) (ps peerSummary, connSummaries []connectionSummary, err error) {
if err = dec.Decode(&ps); err != nil {
return
}
if err = dec.Decode(&connSummaries); err != nil {
return
}
return
}
func makeConnsMap(peer *Peer, connSummaries []connectionSummary, byName map[PeerName]*Peer) map[PeerName]Connection {
conns := make(map[PeerName]Connection)
for _, connSummary := range connSummaries {
name := PeerNameFromBin(connSummary.NameByte)
remotePeer := byName[name]
conn := newRemoteConnection(peer, remotePeer, connSummary.RemoteTCPAddr, connSummary.Outbound, connSummary.Established)
conns[name] = conn
}
return conns
}
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